In industrial bandsaws used for high precision, high volume output, considerable care has to be taken in order to optimize wear on the bandsaw blades. Since high-strength alloy metals are often cut using such saws, the blades often must be carbide or other hard materials capable of cutting such workpieces. Thus, the cost of industrial bandsaw blades is significant, and the cost associated with shutting down production from the bandsaw while a blade is being replaced is also significant.
Two commonly occurring problems can significantly reduce the life of a bandsaw blade. First, there is the problem of saw blade break-in. Second, blade life can be significantly reduced by bandsaw blade break-through.
If a bandsaw is operated at a constant pressure with a brand new blade, the saw will begin cutting at a first cutting rate and then the cutting rate will increase as the blade dulls slightly and begins cutting more efficiently. Over time, the bandsaw blade will dull further and the cutting rate will slow down. Thus, some dulling of the initially very sharp bandsaw blade is desirable in terms of increasing cutting efficiency. However, if a new bandsaw blade is operated at the nominal or desired cutting rate for a given workpiece, such high speed operation can unduly stress and even break or tear teeth on the blade. Moreover, high speed operation also can cause the blade teeth to become dull in an uneven manner. Thus, teeth may dull on one side or the other, rather than evenly across the tooth, and cause the blade to begin to pull away from a straight-line cut. With time, such uneven blade wear tends to become accentuated, which further tends to pull the blade during cutting and reduce the cutting life during which the blade will cut within acceptable tolerances.
It is known in the bandsaw industry that operation of a bandsaw blade during a break-in period at a cutting rate which is below the nominal or desired optimal cutting rate for production cutting will result in an eventual enhancement of production cutting efficiency and a more even dulling of the cutting blade teeth, with an attendant increase in blade life. What has been done in practice, therefore, is to manually set the bandsaw cutting rate at a level which is significantly below the optimal production cutting rate for the workpiece and thereafter periodically manually adjust the cutting rate up to the desired production rate. This break-in technique requires operator training, and predictably some operators are not reliable in their attention to using a break-in cutting rate or to increasing the same over time in an optimal fashion to the production rate.
The problem of bandsaw break-through is related to bandsaw-break-in in that it also can significantly shorten blade life. As a bandsaw blade is exiting a workpiece, there is a thin section of the workpiece material just before the cut is completed. At production feed rates, the bandsaw blade teeth can punch through the thin workpiece section suddenly, which dramatically loads or stresses the teeth and can fracture edges of the teeth. Carbide bandsaw blades are particularly susceptible to this problem in that carbide is strong in the compression loading experienced by normal cutting but not as strong in tension loading which occurs upon break-through. The break-through phenomenon also can effect the quality of the resulting workpiece, but that is generally less of a problem than the effect of break-through on saw blade life.
Again, some operators have manually reduced the saw blade feed rate just prior to exiting the workpiece. This reduction in feed rate reduces the force and depth of the workpiece section at which the teeth finally punch through the workpiece. Such feed rate reduction is known to be effective in reducing break-through saw blade damage, but in industrial bandsaw settings, operators simply are not able to be as attentive to this problem as would be desirable optimally. One compromise approach which is sometimes taken is to reduce the production cutting rate somewhat so as to lessen the break-through problem, but this obviously compromises the optimum production output.
Accordingly, it is an object of the present invention to provide a controller for a bandsaw which is capable of optimal control of both the break-in and the break-through feed rates of the bandsaw cutting blade so as to enhance bandsaw blade life.
Another object of the present invention is to provide a method for controlling the rate of cutting of a bandsaw blade during one or both of bandsaw break-in and bandsaw break-through so as to increase bandsaw blade life.
A further object of the present invention is to provide a method and apparatus for automated break-in of the cutting blade of a bandsaw so that damage to the blade teeth during break-in is avoided and blade life is optimized.
Still a further object of the present invention is to provide a controller and method of operating a bandsaw which will yield improved cutting characteristics in the cut workpiece, reduce operator error, and enable attainment of optimum production cutting speeds in a minimum amount of time.
The apparatus and method of the present invention have other objects, features and advantages which will become apparent from and are set forth in more detail in the accompanying drawing and following description of the Best Mode of Carrying Out the Invention.